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Problems


IDDescription / TitleSolved By
1Multiples of 3 and 5
385670
2Even Fibonacci numbers
318785
3Largest prime factor
232978
4Largest palindrome product
211907
5Smallest multiple
225180
6Sum square difference
226904
710001st prime
194549
8Largest product in a series
172171
9Special Pythagorean triplet
170242
10Summation of primes
155976
11Largest product in a grid
117081
12Highly divisible triangular number
106149
13Large sum
112741
14Longest Collatz sequence
110641
15Lattice paths
92106
16Power digit sum
115547
17Number letter counts
76039
18Maximum path sum I
74421
19Counting Sundays
68665
20Factorial digit sum
105046
21Amicable numbers
73823
22Names scores
68948
23Non-abundant sums
51892
24Lexicographic permutations
59562
251000-digit Fibonacci number
80581
26Reciprocal cycles
42481
27Quadratic primes
44783
28Number spiral diagonals
59149
29Distinct powers
53782
30Digit fifth powers
57076
31Coin sums
42297
32Pandigital products
36366
33Digit canceling fractions
37499
34Digit factorials
49745
35Circular primes
45466
36Double-base palindromes
48288
37Truncatable primes
38530
38Pandigital multiples
32747
39Integer right triangles
37926
40Champernowne's constant
42423
41Pandigital prime
35449
42Coded triangle numbers
40519
43Sub-string divisibility
30240
44Pentagon numbers
29126
45Triangular, pentagonal, and hexagonal
38486
46Goldbach's other conjecture
31065
47Distinct primes factors
29726
48Self powers
63979
49Prime permutations
29483
50Consecutive prime sum
31691